The invention relates to a take-up assembly for automatic film loading of camera, and more particularly, to a take-up assembly including a pawl adapted to engage a perforation in a perforated roll film to take up the roll film while drawing it out of a film magazine.
As is well recognized, a mechanism which is used to load a roll of film automatically into a camera can be categorized into two types, one utilizing the friction occurring between a film and a frictionable member such as rubber to load a leader portion of the film onto a take-up spool, and another which utilizes a pawl mounted on the take-up spool and which is adapted to engage a perforation in the film to load the leader portion onto the spool.
In the former arrangement utilizing a frictional member, the rubber material which forms the frictional member has a durability which is less than desired. Hence, even though such mechanism can be practically implemented, the reliability is reduced and the mechanism cannot be used over a prolonged period of use. The use of resilient means to increase the friction between the film and the frictional member is also known, but results in a complex arrangement and vulnerability of the film.
In the latter arrangement utilizing the pawl mounted on the take-up spool, a uniform film winding is not achieved in that during a second turn, a portion of the film is placed over the pawl. In other words, the film of roll is not wound in a truely circular form, but as viewed circumferentially, a portion of the film roll bulges outwardly, resulting in a pool planarity of the film to damage the film or cause an increased load during a film take-up operation.
In addition, it is difficult to achieve an automatic engagement of the pawl with one of the perforations, and the arrangement fails to provide an automatic loading unless the pawl is previously engaged with one of the perforations. If the pawl is engaged with one of the perforations beforehand, the pawl is liable to be disengaged upon initiating the rotation of the spool, causing a difficulty in the operational reliability.
To eliminate the foregoing disadvantages, there has been proposed a take-up assembly for automatic loading of a perforated roll of film as shown in FIG. 1. In this Figure, a perforated roll of film 1, hereafter simply referred to as a film, is formed with perforations 1a adapted to be engaged by a pawl 2a of a catch member 2 which is arranged in a recess 4, formed in a take-up spool 3. The catch member is normally urged by a spring 5 to project out of the recess 4. The arrangement is intended to assure that the pawl 2a automatically engages one of perforations 1a so that the catch member 2 is driven into the recess 4 by the tension in the film 1 as the latter is pulled by the rotation of the take-up spool 3.
However, the described take-up assembly 6 is constructed such that the pawl 2a normally projects beyond the outer diameter of the take-up spool 3 when the film 1 is not disposed thereon. This makes the catch member 2 susceptible to deformation. In particular, as when the take-up spool 3 is rotated in the reverse direction, the pawl 2a may rub against the inner wall of the spool chamber formed in the camera, producing an unpleasant sound resulting from friction, or may be trapped by part of the inner wall to render the rotation of the take-up spool 3 in the reverse direction impossible. Alternatively, if the take-up spool 3 is reversed when the pawl 2a is jammed, the catch member 2 may be disadvantageously broken or deformed. To prevent the pawl 2a from rubbing against the inner wall of the spool chamber, it must be disposed toward the spool 3. However, in this instance, the pawl will engage the perforation 1a formed in the film 1 at a location displaced toward the center of the spool, as viewed lengthwise thereof, disadvantageously causing an unreliable film take-up operation unless an increased length of film 1 is previously withdrawn from the magazine.